Phenolic acids, decarboxylation

It seems most likely that the presence of the styrene compound was at least partially responsible for the inhibition of prickly sida germination and root length, since ferulic acid alone (prickly sida seed without carpels plus ferulic acid) had no effect on prickly sida germination or root length (Table XI). The decarboxylation of phenolic acids to corresponding styrenes is known from studies on fungi and bacteria (60, 61). However, in a number of studies directly concerned with the microbial decomposition of ferulic acid, as well as other phenolic acids, no mention is made of any styrene compounds produced as a result of phenolic acid decarboxylation (62, 63, 64, 65). 

Chatonnet, R, Dubourdieu, D., Boidron, J. N. (1989). Effects of certain factors on yeast phenolic acid decarboxylation. Conn. Vigne Vin., 23, 59-62. 

Phenolic acids are often found in plant tissue, and have been implicated in many cases of allelopathy (4). Figure 6 shows a separation of three free phenolic acids and Figure 7 shows mass spectra obtained from these compounds. These spectra give both molecular weight and structural information. Phenolic acids can easily be thermally decarboxylated. The height of the molecular ion peak varies owing to ion source temperature. The variation depends also to some extent on the composition of the LC eluent, and this will be further examined. 

Grape compounds which can enter the yeast cell either by diffusion of the undissociated lipophilic molecule or by carrier-mediated transport of the charged molecule across the cell membrane are potentially subject to biochemical transformations by enzymatic functions. A variety of biotransformation reactions of grape compounds that have flavour significance are known. One of the earlier studied biotransformations in yeast relates to the formation of volatile phenols from phenolic acids (Thurston and Tubb 1981). Grapes contain hydroxycinnamic acids, which are non-oxidatively decarboxylated by phenyl acryl decarboxylase to the vinyl phenols (Chatonnet et al. 1993 Clausen et al. 1994). 

The formation of the phenoxide anion enhances the reactivity of the ortho and para positions of the aromatic ring towards electrophilic reagents. The reaction of the phenoxide anion with carbon dioxide at 130 °C leads to ortho carboxylation (the Kolbe reactior. Thus phenol gives salicylic acid (4.4), the acetate of which is aspirin. The reaction is reversible and ortho phenolic acids undergo decarboxylation on heating. 

The data for this solvent were not used to calculate the parameters in Table 54. Similarly the data for decarboxylation of oxanilic acid in anisole were not used for the AH -AS correlation. With the reported AH value of 32.6 kcal.mole , the entropy of activation is calculated to be 3.59 0.03 eu compared to the reported value of 11.1 eu. In the decarboxylation of malonic acid, the data obtained with pyridine and ) -mercaptopropionic acid solvents deviated considerably from the plots and were not included in the correlation. The data for malonic acid decarboxylation appeared to be best correlated by two lines. One line was described by the following solvents acids, phenols, nitro-aromatics, benzaldehyde, and the melt the other line involved amines, alcohols, dimethylsulfoxide and triethyl phosphate. The latter line was not as well defined as the former. However, it was our intention to correlate as many solvents as possible with a minimum number of lines. The data for decarboxylation of malonic acid in water and in benzyl alcohol fell between these two lines and were not included in either correlation. The data for decarboxylation of benzylmalonic acid also appeared to be best correlated with two lines. One line was defined by the cresols, acids and the melt, while the other line was defined by the amines. Decarboxylation of cinnamalmalonic acid was correlated by two lines as indicated in Table 54. Similarly j8-resorcylic acid was correlated by two lines. The separation of data into parallel lines is presumably due to multiple solvation mechanisms . In support of this interpretation it is seen that when two lines are observed, acids fall into one line and amines into the other. It is not unexpected that the solvation mechanisms for these two classes of solvents would differ. It is interesting to note that all of the nitrogen containing acids are correlated reasonably well with one line for both basic and acidic solvents. Also the AHq values fall in a rather narrow range for all of the acids. From the values of p in Table 54, there appears to be little correlation between this parameter and the melting point of the acids, contrary to prior reports " ... 

Decarboxylase Decarboxylation of amino acids and simple phenolic acids, primarily p-hydroxylated L-Dopa, tyrosine... 

Volatile phenols can be produced by microorganisms from the decarboxylation of phenolic acids such as ferulic and coumaric, and tyrosine(27). Phenols may contribute to the dryness characteristics in scotch whiskey(25). Cresols and guiacols have been reported to have an effect on the aroma of whiskeys(28). 

A scheme for the formation of guaiacols from ferulic acid has also been proposed by Manley et al. (1974). The biosynthesis of various phenolic acids from p-coumaric acid (H.84) was studied by Friedrich (1976). Formation pathways for simple phenols in food flavors have been reviewed (Maga, 1978a). The two primary pathways could be the decarboxylation of phenolic carboxylic acids and the thermal degradation of lignin. Secondary pathways include bacterial, fungal, yeast enzymic and glycosidic reactions. 

Phenolic acid derivatives (cinnamic acids) and degradation products of flavonoids (phenylpropionic and phenylacetic acids) suffer transformations by caecal bacteria. The following transformations have been observed dehydroxylation of 3,4-dihydroxy derivatives to give 3-hydroxy compounds, demethylation of o-hydroxy-methoxyphenolic acids, reduction of the double bonds of cinnamic acids to yield the corresponding phenylpropionic acids, decarboxylation of cinnamic and phenylacetic acids (only when 4-hydroxyl is present), hydroxylation of... 

Fig. 8.6. Decarboxylation of phenol acids in must by Saccharomyces cerevisiae during alcoholic fermentation...

Poly(benzimidazoles) are produced from dicarboxylic acids and aromatic tetramines. Commercially, 3,3 -diaminobenzidine tetrahydrochloride and diphenyl isophthalate are preferentially used. The diphenyl ester is used because (a) the free acids decarboxylate under the high reaction temperatures of 250-400 C (b) the acyl chlorides react too fast, making ring closure difficult and (c) the amino groups are partially methylated if the methyl esters are used. The hydrochloride is used because it is more stable to oxidation than the free amine itself. The polycondensation is carried out in two stages. A prepolymer. A, is formed in the first stage with foaming and phenol elimination ... 

Some phenolic acids like caffeic acid, p-coumaric acid and ferulic acid can act as precursors of volatile phenols, which could contribute positively to wine aroma, when they are present at low concentrations associated descriptors are smoky, dove-like and leather (Table 1). Yeasts can conduct the decarboxylation of phenolic adds to volatile phenols, as well as esterase activities present in enzymatic preparations used in winemaking. During wine storage and ageing, volatile phenols may be further transformed. 

Poly(benzimidazoles) have become commercially important. Whereas polyimides contain two carboxyl groups per amine group, two amine groups are allowed to react with a carboxyl group in poly(benzimidazole) manufacture. Diphenyl esters are used as dicarboxyl compounds, since (a) the free acids decarboxylate under the reaction conditions (250°C at first, subsequently 400°C), (b) the acyl chlorides react too quickly, so that ring closure becomes difficult, and (c) with methyl esters, the amino groups become partially methylated. Moreover, eliminated phenol can easily be washed out. Typical materials are 3,3 -diaminobenzidine and diphenyl... 

P-orcinol series The orcinol-type compounds discussed in the previous section form a closely related series of substances in which changes in the length and oxidation state of the 6-alkyl substituents are major sources of variation among phenolic units. The compounds synthesised by various combinations of these units show secondary modifications attributable to 0-methylation, chlorination, decarboxylation and lactonisation. The p-orcinol compounds may undergo all of the same secondary reactions, but the most common variation is in the oxidation state of the Cj substituents at the 3- and 6-positions of the phenolic acid units. 

Lichen monoaryl derivates are relatively rare in lichens. All of the lichen monoaryl derivates have lost their free carboxylic acid groups either by esterification or by decarboxylation. These compounds might be synthesised in the lichen from coenzyme A derivates of the initially formed phenolic acid units or by biological decomposition of depsides. 

Bernini, R., Mincione, E., Barontini, M., Provenzano, G. and Setti, L. 2007. Obtaining 4-vinyl-phenols by decarboxylation of natural 4-hydroxycinnamic acids under microwave-irradiation. Tetrahedron. 63 9663-9667. 

Synthetic phenol capacity in the United States was reported to be ca 1.6 x 10 t/yr in 1989 (206), almost completely based on the cumene process (see Cumene Phenol). Some synthetic phenol [108-95-2] is made from toluene by a process developed by The Dow Chemical Company (2,299—301). Toluene [108-88-3] is oxidized to benzoic acid in a conventional LPO process. Liquid-phase oxidative decarboxylation with a copper-containing catalyst gives phenol in high yield (2,299—304). The phenoHc hydroxyl group is located ortho to the position previously occupied by the carboxyl group of benzoic acid (2,299,301,305). This provides a means to produce meta-substituted phenols otherwise difficult to make (2,306). VPOs for the oxidative decarboxylation of benzoic acid have also been reported (2,307—309). Although the mechanism appears to be similar to the LPO scheme (309), the VPO reaction is reported not to work for toluic acids (310). 

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